Photo‐Carrier Recombination in Polymer Solar Cells Based on P3HT and Silole‐Based Copolymer

Photo‐current loss in donor‐acceptor (DA) polymer‐fullerene bulk heterojunction solar cells was studied via carrier transport and recombination measurements. Focusing on the DA polymer poly((4,4‐dioctyldithieno (3,2‐b:2',3'‐d) silole)‐2,6‐diyl‐alt‐(2,1,3‐benzothiadiazole)‐4,7‐diyl) (DTS‐BTD) we found that the carrier transport is well‐balanced and attribute the loss mechanism in DTS‐BTD solar cells to carrier recombination. Using carrier extraction with linear increasing voltage (photo‐CELIV) and transient photo‐voltage (TPV), we show that carrier recombination plays an important role in photo‐current extraction at open circuit conditions due to increase in photo‐excited carrier concentration. Delay time dependent photo‐CELIV and temperature dependent transport studies suggest that the recombination rate is related to the degree of energetic disorder in the polymer: fullerene blends.     

Abortive autophagy induces endoplasmic reticulum stress and cell death in cancer cells

Autophagic cell death or abortive autophagy has been proposed to eliminate damaged as well as cancer cells, but there remains a critical gap in our knowledge in how this process is regulated. The goal of this study was to identify modulators of the autophagic cell death pathway and elucidate their effects on cellular signaling and function. The result of our siRNA library screenings show that an intact coatomer complex I (COPI) is obligatory for productive autophagy. Depletion of COPI complex members decreased cell survival and impaired productive autophagy which preceded endoplasmic reticulum stress. Further, abortive autophagy provoked by COPI depletion significantly altered growth factor signaling in multiple cancer cell lines. Finally, we show that COPI complex members are overexpressed in an array of cancer cell lines and several types of cancer tissues as compared to normal cell lines or tissues. In cancer tissues, overexpression of COPI members is associated with poor prognosis. Our results demonstrate that the coatomer complex is essential for productive autophagy and cellular survival, and thus inhibition of COPI members may promote cell death of cancer cells when apoptosis is compromised.     

Mountain-associated clade endemism in an ancient frog family (Nyctibatrachidae) on the Indian subcontinent

Night frogs (Nyctibatrachidae) form a family endemic to the Western Ghats, a hill chain along the west coast of southern India. Extant members of this family are descendants of a lineage that originated on the subcontinent during its longtime isolation in the Late Cretaceous. Because the evolutionary history of Nyctibatrachidae has always been tightly connected to the subcontinent, these tropically-adapted frogs are an ideal group for studying how patterns of endemism originated and evolved during the Cenozoic in the Western Ghats. We used a combined set of mitochondrial and nuclear DNA fragments to investigate the phylogenetic relationships of 120 ingroup specimens of all known species of Nyctibatrachidae. Our analyses indicate that, although this family had an early origin on the Indian subcontinent, the early diversification of extant nyctibatrachids happened only in the Eocene. Biogeographic analyses show that dispersal across the Palghat gap and Shencottah gap was limited, which led to clade endemism within mountain ranges of the Western Ghats. It is likely that multiple biota have been affected simultaneously by these prominent geographical barriers. Our study therefore further highlights the importance of considering the Western Ghats-Sri Lanka biodiversity hotspot as an assemblage of distinct mountain regions, each containing endemism and deserving attention in future conservation planning.     

Expression pattern of Glycoconjugates in Rat Retina as Analysed by Lectin Histochemistry

The present study sought to characterize the expression and distribution of complex glycoconjugates in the rat retina by lectin histochemistry, using a panel of 21 different lectins with different carbohydrate specificities. Paraffin sections of Carnoy-fixed Sprague–Dawley rat eyes were stained with various biotinylated lectins, followed by the streptavidin-peroxidase and glucose oxidase–diaminobenzidine–nickel staining procedures. The results showed that the retinal pigment epithelium was stained intensely with LCA, Jacalin, WFA, S-WGA, PWA, DSA, UEA-I, LTA and PHA-E, suggesting that this epithelium contained glycoconjugates with α-Man, α-Glc, α-Gal/GalNAc, β-GalNAc, α-Fuc, NeuAc and other oligosaccharide residues. The outer and inner segments of the photoreceptor layer showed different lectin binding affinities. The outer segments reacted with S-WGA and GS-II, whereas the inner segments reacted with UEA-II, UEA-I, LTA and MAA, suggesting that the inner segments contained glycoconjugates rich in α-Fuc and NeuAc(α2,3)Gal residues. PNA labelled specifically the cones and could be used as a specific marker for these photoreceptors. RCA-I, WFA, S-WGA, DSA, MAA and PHA-E reacted with both the outer and inner plexiform layers. On the other hand, UEA-I and LTA specifically labelled the outer plexiform layer, while PNA labelled the inner plexiform layer. The retinal microglial cells were labelled specifically by GS-I-B₄ and SNA. Interestingly, we also observed that WFA bound specifically to Müller cells and could be used as a novel marker for this retinal glial cell. The capillaries and larger vessels in the retina and choriocapillaris reacted intensely with GS-I-B₄, RCA-I, S-WGA, PWA, DSA and PHA-E. No significant differences in lectin binding were observed in the microvessels at these two sites. In summary, the present study demonstrated the expression patterns of glycoconjugates in the rat retina and that certain lectins could be used as histochemical markers for specific structural and cellular components of the rat retina.